Many industries, not least among them the food industry, find it necessary in the course of their operations to be able to cool or heat products relatively rapidly.
When a product needing chilling or freezing is at room temperature, or is at temperatures higher than room temperature as the result of a previous processing or cooking step, reducing the temperature of the product rapidly is desirable in order to minimize the ability of pathological organisms such as bacteria to grow on or in a product, and (particularly when the product is to be frozen), to put the product into condition to be packaged prior to its being stored and/or shipped to distributors or customers. Examples of products which benefit from this treatment, which are also products that can be treated by the present invention, include raw foods such as eggs, hamburger patties, fruits and vegetables, raw or cooked cuts of meat such as beef, pork, veal, lamb, poultry carcasses and poultry sections, as well as processed foods prepared by combining various ingredients, such as pastries, pre-packaged entrees and complete dinners.
When a product is to be heated or cooked, the ability to achieve the necessary heat transfer rapidly is useful in order to minimize the opportunity for pathogens to grow, and to achieve a greater rate of processing in a given period of time.
Many techniques are known for cooling and freezing large numbers of food products. Examples include impingement coolers, mechanical refrigerators, and other devices wherein the product is conveyed through a chamber wherein the product is exposed to low temperatures for a sufficient period of time to reduce the temperature of the product to the desired final, cooled temperature.
Many techniques are also known for heating and cooking large numbers of food products, such as tunnel ovens and the like.
One preferred type of device applicable to cooling/freezing and heating/cooking applications is known as a spiral or helical cooler or cooker, wherein at least a portion of the path that the product follows as it is conveyed through a chamber is in the form of a helix. For example, the product is placed on a moving flexible belt that follows a path which curves around on itself as it steadily climbs. With this type of device, the product travels a longer distance and experiences a longer dwell time in the cooling or heating environment for a given amount of area occupied by the device, taking advantage of the vertical array of the belt.
Helical (or spiral) devices have heretofore presented a drawback that the successive tiers of the belt interfere with heat transfer from or to the product, because of the proximity of adjacent tiers which interfere with flow of cooling or heating air and which are also carrying product that as a heat sink or source, as the case may be
Thus, there remains a need for devices and methods that retain the advantages of helical devices but which achieve faster heat transfer to or from the product than has been available up to now.